There are a variety of “backlight-and-panel” displays. These displays often include one or more backlights behind a panel of tiny, electrically-controllable “shutters.” These shutters can be implemented in a number of different ways using a variety of technologies. The shutters can form dots, or pixels, of light on a panel by passing light from the backlight(s). The amount of light passed by each dot can be controlled by “opening or closing” the respective shutter to varying degrees. Depending on the technology being used, the shutters may not mechanically open and close in a literal sense, but the shutters can nevertheless be electrically controlled to provide that effect. A panel may include many thousands of these shutters that can be individually controlled to collectively form images. The data that indicates which shutters to open and close, and to what extent, is referred to herein as “image data.”
In a color display, each pixel in a panel usually includes a group of at least three shutters, and the backlight often provides a wide spectrum of light. Each shutter in a group of three may be filtered to pass a different color of light from the backlight. For example, one shutter may pass red light, one shutter may pass green light, and one shutter may pass blue light. In which case, by individually controlling the three shutters in a pixel, different amounts of red, blue, and green light can be mixed to provide a wide variety of colors.
Backlight-and-panel displays are commonly used in a variety of mobile electronic devices, such as notebook computers, personal data assistants, cell phones, and the like. Unfortunately, backlights tend to consume a relatively large amount of power and can substantially shorten the battery life of a typical mobile device. A number of techniques have been developed to dim backlights under various circumstances to save power and extend battery life. One of these techniques is sometimes referred to as backlight modulation (BLM) or backlight image adaptation (BIA), but will be referred to as display power saving technology (DPST) for purposes of this patent.
The image data for a display panel is usually generated based on the backlight brightness level, also called the backlight setting. For a particular set of image data and a particular backlight setting, a vast majority of the shutters in a panel may be less than fully open. DPST technology can take advantage of this situation to save power by reducing the backlight setting and adjusting the image data to maintain or approximate the same perceived brightness level. That is, DPST technology can turn down the backlight to save power and compensate for much of the reduction in the backlight setting by opening shutters to a greater extent. DPST can analyze various characteristics of an image on a display, such as color, contrast, brightness, etc., to determine how much to adjust the image data and how much to adjust the backlight setting.